A mobile terminal such as a mobile phone, a personal digital assistant (PDA), or the like is powered by a rechargeable battery, and a battery of the mobile terminal is charged by using a separate charging device. In general, separate contact terminals are placed outside each of the charging device and the battery, and the charging device is electrically connected with the battery by electrically connecting the separate contact terminals with each other.
Recently, a wireless charging technology or a non-contact charging technology have been developed and have been used for a large number of electronic devices. A wireless power transmission technology that is currently commercialized or is being studied may be roughly divided into four types.
One of them is a high power microwave radiation method. This method may be used for long-range transmission because it is possible to transmit high power by using a frequency of a few GHz. However, the one has not been commercialized due to harmfulness to human body, straightness, and the like. Another of them is a radiative short-range transmission method of a radiative manner. This refers to a radio-frequency identification (RFID) service using a RFID/USN frequency band of an ultra-high frequency (UHF) or an ISM band of 2.4 GHz. This is currently commercialized in a specific field such as a distribution field, a logistics field, or the like. This may only transmit power of maximum dozens milliwatts due to radiation loss. In addition, an extension of a RFID standard is exemplified as an ultra-short range wireless communication technology such as NFC.
Meanwhile, a contact-type transmission method using inductive coupling refers to a method for transmitting electric power of a few watts in a contact manner at a spaced distance of a few millimeters to a few centimeters, and uses a frequency of 125 kHz, 135 kHz, or the like. Now, the method may be applied to a traffic card, a wireless shaver, an electric toothbrush, and the like.
In addition, the nonradiated magnetic resonance method is based on a resonant coupling method. Resonant coupling refers to a phenomenon in which an electromagnetic wave propagates from one medium to another medium through a short-range magnetic field when the two media resonate at the same frequency in the case of magnetic resonance. The method may transmit power of dozens watts within a spaced distance of a few meters. However, to implement the method, it is necessary to keep a value of a quality factor (Q) of the resonator high.
In the meantime, a large number of mobile terminals equipped with an NFC module for NFC communication have been recently released.
NFC is a proximity communication technology for transmitting and receiving data at a distance of about 10 cm using a frequency of 13.56 MHz. The NFC module mounted in the mobile terminal is used in various fields such as user authentication, an identifier (ID) card, a credit card, a mobile ticket, a mobile coupon, and the like. An NFC antenna is required for the NFC communication. The NFC antenna includes each of an NFC reader antenna and an NFC tag antenna. In the case where the NFC antenna is actually implemented on the mobile terminal, an integrated dual antenna structure in which the NFC reader antenna and the NFC tag antenna are stacked is generally used.
Korean patent publication No. 10-2013-0053856 relates to the wireless power receiver and a control method thereof and discloses a technology associated with a wireless power receiver that wirelessly receives power based on an electromagnetic resonance method and a control method thereof.
However, nowadays, a method for supporting all of magnetic induction, magnetic resonance, and NFC using one resonance coil is required.